Parallel assisted circuit interruption device with interlock



Aug. 11, 1970 H. G WILLARD' 3,52

PARALLEL ASSISTED CIRCUIT IN'LEHHU["I'1UN DEVICE WITH INTERLOCK Filed June 20, 1967 2 Sheets-Sheet 1 N VEW TOR. HEW/3 Y G W141 A/ea ATTORNEY 8" 11, 0 H. G. WILLARD PARALLEL ASSISTED CIRCUIT INTERRUPTION DEVICE WITH INTERLOCK Filed June 20, 1967 2 Sh'eets- Sheet 2 /NVNTOR HENRY G W/LLARD BY w f v A TTOR/VEY United States Patent 3,524,104 PARALLEL ASSISTED CIRCUIT INTERRUPTION DEVICE WITH INTERLOCK Henry G. Willard, Wethersfield, Conn., assignor to General Electric Company, a corporation of New York Filed June 20, 1967, Ser. No. 647,505 Int. Cl. H02h 7/22 US. Cl. 317-11 1 Claim ABSTRACT OF THE DISCLOSURE A circuit interrupter has a controlled-breakdown gap device (such as a triggered vacuum gap device) connected in parallel with it in such a way that as its contacts open, the arc voltage appears as triggering voltage to cause breakdown of the parallel connected device; continued opening movement of the interrupter contact arm opens contacts in series with the breakdown device trigger so that triggering is not caused by line voltage in the open condition of the interrupter.

The present invention relates to electric current interrupting devices, and, more particularly, to devices of the type in which electric current in a load-carrying circuit is interrupted in a main circuit path with the assistance of a parallel circuit path which aids in the carrying and dissipation of currents, which are to be interrupted. For convenience, this technique of circuit interruption is referred to as parallel assisted circuit interruption.

In the US. Pat. No. 3,087,092, Lafferty, issued Apr. 23, 1963, and assigned to the same assignee as the present invention, there is disclosed a preferred type of device for use in a parallel current interruption assisting path. This is a controlled breakdown gap device which has a pair of current-carrying terminals and a control electrode. Normally, the device is nonconducting; however, upon the application of a sufficient triggering voltage between the control conductor and one of the main current-carrying terminals, the device is transformed into a currentcarrying state in which electric current flows between the main terminals therein. Removing the triggering voltage from the control electrode permits the current to go to zero during a first current null; such as within a quarter cycle of a current peak in an AC circuit.

A similar device having a pair of control electrodes is described in US. Pat. No. 3,030,376, Lafferty, issued Feb. 7, 1967, and assigned to the same assignee as the present invention, wherein each of a pair of control electrodes is associated with one of the main current-carrying terminals and wherein a suitable potential applied across either of the control electrodes and its associated main currentcarrying terminal will cause the device to break down so that current will transfer between the main current-carrying terminals. These devices are preferably used in series with current-limiting resistances that limit the magnitude or peak current after transfer. Thus, when current is interrupted by a circuit breaker in a load-carrying line, either of these devices may be triggered so as to assist in carrying the interruption current and reducing the current to zero.

The application of these devices in a parallel assisted current interruption apparatus is disclosed in a copending application of Hurtle, Ser. No. 542,806, filed May 15, 1966, and assigned to the same assignee as the present invention. Therein, the high are voltage created by a circuit interrupter having a diverging arc runner is utilized to supply the triggering potential for the controlled breakdown gap device.

It is an object of the present invention to provide a novel parallel circuit electric current interrupting device which is relatively simple and yet very eliective and which permits electrical coupling of the parallel circuit device ice only during periods when current interruption is contemplated.

Another object is to provide a device having relatively simple and effective means for connecting and disconnecting the parallel circuit device to the main circuit device.

Still another object is to provide such a device which may be readily constructed, which utilizes relatively few parts, and which is relatively long-lived.

Other objects of the invention will in part be pointed out in the following detailed description and in part will become obvious from the following detailed description of specific embodiments of the invention, and the scope of the invention will be pointed out in the appended claims.

It has now been found that the foregoing and related objects can be readily attained in an electric circuit interrupter wherein an electric circuit breaker is combined with an interruption-assisting device and with a switch in the connection therebetween having contacts and a movable actuating member adapted to open and close the contacts. The movable actuating member is operatively connected to the circuit breaker so as to open the contacts of the switch after opening of the contacts of the circuit breaker.

More particularly, the electric circuit breaker has a fixed contact and a movable contact with suitable actuating mechanism and is connected in series between two points of an electric current-carrying circuit to be controllably interrupted by the circuit interrupter. The interruption assisting device includes at least two main conducting terminals and a control means actuatable upon the impression of a sufiicient predetermined voltage thereacross to change the device from a normally substantially nonconducting condition to a conducting condition in which current is conducted by the main conducting terminals. Upon cessation of the current between the main conducting terminals in the absence of the predetermined voltage across the control means, the interruption assisting device returns to the normally nonconducting condition.

Control circuit means connect the control means of the interruption assisting device through the switch across the contacts of the circuit breaker so that the voltage appearing across the contacts of the circuit breaker will be connected to the control means, thereby providing the predetermined voltage across the control means upon a substantial change in current flowing through the current breaker. In addition, circuit means connect each of the main conducting terminals of the interruption assisting device to one of the two points, respectively, of the electric current-carrying circuit so that current passing between the main conducting terminals will shunt the circuit breaker.

In its preferred form, the switch is simply constructed and mechanically connected to the actuating mechanism of the circuit breaker so that the contacts will open after a delay following opening of the circuit breaker contacts. It will be apparent that two sets of contacts may be provided and that each of the sets of contacts may be connected to a control electrode in the control means. The mechanical linkage may include a lost-motion connection of a variety of forms and the actuating member may simply be disposed in the path of movement of the actuating mechanism of the circuit breaker so that it will be actuated thereby only after a predetermined amount of movement of the actuating mechanism of the circuit breaker.

The control means of the interruption assisting device may assume a variety of forms. In one embodiment it is a control electrode cooperating with one of the main conducting terminals to initiate the conducting condition upon the application of the predetermined voltage between the main conducting terminals. In another form it includes a pair of control electrodes cooperating with each other to initiate the conducting condition upon the application of the predetermined voltage between them. In still another embodiment, it includes a pair of control electrodes for each pair of main conducting terminals with the control electrodes of each pair each cooperating with one of each pair of main conducting terminals to initiate the conducting condition upon the application of the predetermined voltage between them.

It will be appreciated that various components of the circuit interrupter may be duplicated depending upon the requirements of the circuit and that, although a single element or pair of elements may be recited, a greater number is intended to be encompassed thereby.

Thus, the potential of an arc in an arc chute may provide the voltage to activate the interruption-assisting device by providing electrodes on terminals in the arc chute as shown in the aforementioned application of Hurtle, Ser. No. 542,806. However, other means of effecting the potential required to trigger the control circuit means may be employed including line voltage transferred through it as the breaker is being tripped. It can be seen that the present invention isolates the interruption-assisting device when the circuit breaker is opened manually, or when it has been tripped so that it will be elfective to terminate the arc and interrupt the circuit as the current goes to zero.

The invention will be more fully understood from the following detailed description, and its scope will be pointed out in the appended claims.

In the drawings,

FIG. 1 is a semidiagrammatic illustration of an electric circuit interrupting device embodying the present invention and utilizing a controlled breakdown gap device having a single control electrode and shown in solid line in the normal, closed circuit position;

FIG. 2 is a semidiagramm'atic illustration of the embodiment of FIG. 1 shown in the open or operated position;

FIG. 3 is a schematic diagram of a portion of another embodiment of circuit interrupting device in which a pair of control electrodes cooperate to control the breakdown of the device; and

FIG. 4 is a schematic diagram similar to FIG. 3 of a portion of still another embodiment in which a double controlled breakdown gap device having two control electrodes is utilized.

Referring now in detail to FIG. 1, the invention is shown as incorporated in an electric circuit interrupting device having a line terminal and a load terminal 11 and comprising a main circuit breaker generally designated by the numeral 12 and a controlled breakdown gap device generally designated by the numeral 13. In accordance with generally conventional construction, the circuit breaker 12 includes a fixed contact 40 and a movable contact 42 which is carried by the contact arm 44 for movement about the pivot 46 into closed and open circuit positions. Attached to the contact arm 44 is the lower link 48 of a toggle mechanism which also includes the upper link 50 pivoted to the lower link 48 by the pivot pin 52, and a spring 54 which is also attached to a manual operating handle 56 which is pivotable about the point 58. The upper link 50 of the toggle is pivotably attached to a releasable cradle 60 by a pin 62, which in turn is pivotable at one end about the pivot 64. The free or other end of the cradle 60 has a latch shoulder 66 which is normally engaged by the elements of a trip unit 68 maintaining the assembly in the illustrated position. The specific nature of the trip unit 68 of the circuit breaker 12 is immaterial to the present invention since such devices are well-known, and are capable of operating thermally, magnetically, or in response to other automatic means, and in various combinations of such actuating principles.

Whenever excessive currents are sensed, the trip unit 68 releases the latch shoulder 66 and thereby permits the force exerted by the spring 54 through the upper link of the toggle 50 to cause the cradle 60 to rotate clockwise about the pivot 64 thereby permitting the toggle linkage to raise the contact arm 44 and the movable contact 42 into the circuit opening position. The contact arm 44 may also be raised by the movement of the handle 56 from the position shown in FIG. 1 to the position shown in FIG. 2. Movement of the handle 56 to the left causes the pivot 57 to also move to the left, thereby causing the spring 54 to exert a force on the pivot 52 toward the upper left whereby the position of the toggle 48, 50 is changed from the straight condition (FIG. 1) to the collapsed condition (FIG. 2).

Movable by pivoting of the contact arm 44 is the pivoted head 78 of a movable actuating member 70, which carries at its other end a movable switch contact 72 which is normally held in circuit closing relationship with a pair of fixed switch contacts 74, 76 by the force of a compression spring 80 acting against a portion of the frame of the circuit breaker 12. The movable member 70 is mechanically linked to the operating mechanism of the circuit breaker 12 in such a fashion that the contact 42 will move away from the fixed contact 40 towards the circuit opening position (as shown by the phantom line illustration in FIG. 1) prior to the time that the actuating member 70 will be effective to cause the movable contact 72 to move into the open position (as shown in FIG. 2) so that it will be operative during the initial opening of the breaker. This may be achieved as illustrated somewhat diagrammatically in FIG. 1 by locating the head 78 of the actuating member 70 so that it is engaged by the contact arm 44 only after the contact arm 44 has moved a predetermined distance along its predetermined path in response to the urging of the lower link 48 of the toggle linkage.

The controlled breakdown gap device 13 is connected electrically in series with a resistor 14, and the combination of the breakdown gap device 13 and resistor 14 is connected at points 15 and 16 to the line terminal 10 and the load terminal 11 so as to be electrically in parallel with the circuit breaker 12.

The controlled breakdown gap device 13 comprises a pair of main conducting terminals or electrodes 36, 37 and a control electrode 38. This device may be of the form shown in the aforementioned Lafferty Pat. No. 3,087,092 and wherein a complete description of such a device is found which will not be repeated herein. In this device, the application of a sufficient triggering voltage between the control electrode 38 and the currentcarrying electrode 36 initiates a spark discharge between them. As described in said Latferty patent, this causes heating of a titanium hydride film in the vicinity of the arc which releases hydrogen which becomes ionized and creates a highly conducting arc between the electrodes 36, 38. Since this are is also between the electrodes 36 and 37, it substantially reduces the breakdown potential required for conduction across the gap between the electrodes 36, 37. If sufficient voltage exists across the main electrodes 36 and 37, a breakdown will now occur across the main gap between these electrodes, creating an are capable of carrying high current. Once an arc has been established across the main arc gap, a subsequent decrease of such are current to zero, such as, for example, upon the decrease of current in an alternating current circuit to the zero point, will quickly extinguish the arc and the conduction carries or charged particles within the discharge device disappear. As described in said Lalierty Pat. No. 3,087,092 the charged particles are essentially electrons and ionized copper atoms which emanate from the electrodes 36, 37. These charged particles flow to the electrodes or to other portions of the structure within the device where their charge is lost so that they are removed from the conduction area between the electrodes. Since the device is maintained at a high vacuum with essentially no ionized gases normally present, the gap between the main electrodes rapidly recovers and no further current flow is possible until triggering occurs again. Such recovery may occur in a range of from 25 to 100 microseconds after extinction of the arc.

The circuit point 16 is connected through a resistor 50, capacitor 51, and switch contacts 72, 74, and 76 to the control electrode 38. The resistor 50 and the capacitor 51 which are in series with the control electrode 38 limit the current which flows through the control electrode 38 to that which is essential to cause triggering of the controlled breakdown gap device 13.

The resistor 14, which is in series with the controlled breakdown gap device 13, limits the flow of current through the device 13 in order to prevent damage to the device. As described in the aforementioned Hurtle application, Ser. No. 542,806, the resistor 14 is preferably composed of material having a positive temperature coefficient so that the resistance increases rapidly and limits the magnitude of the current. Once the current reaches the next null or zero point in the alternating current cycle, the current is extinguished within the controlled breakdown gap device since the conventional circuit breaker 12 has, by this time, had sufficient time in which to recover dielectric strength and no voltage is then applied to the control electrode 38 since the contacts 72, 74, 76 are then open. Without a continuing control electrode triggering potential, the controlled breakdown gap device 13 is able to cease the flow of current.

Thus, there has been described one embodiment of the invention in its simplest form, in which a controlled breakdown gap device having a single control electrode is triggered by voltage appearing between the line terminal and the load terminal 11 at the instant that the circuit breaker 12 is opened.

In operation, whenever the movable contact 42 is raised above the closed circuit position shown in FIG. 1, whether by actuation of the trip unit 68 and the clockwise rotation of the cradle 60, or by manual movement of the handle 56 from right to left (as shown in FIGS. 1 and 2), it will engage the head 78 of the actuating member 70 and effect movement thereof, thereby causing the movable contact 72 of the switch to move into the open circuit position (as shown in FIG. 2). Since the control electrode 38 is normally connected through the resistor '50 and capacitor 51 to the connection point 16 and the main conducting terminal 36 is connected to connection point 15, any potential which may develop between connection points 15 and 16 will be impressed across the main conducting terminal 36 and control electrode 38.

In normal operation, the circuit breaker 12 is normally closed so that there is substantially no potential between the connection points 15, 16. However, upon movement of the movable contact 42 into the circuit open position (as shown in FIG. 2) there Will be a substantial voltage between the circuit breaker contacts 42, 40 and therefore between the connection points 15, 16. This potential is applied across the control electrode 48 and main conducting terminal 36 until such time as the contact arm 44 has moved sufiiciently along its predetermined path so as to cause the movable member 70 to raise the movable contact 72 into the circuit open position (as shown in FIG. 2). This causes a removal of the control potential, so that, once a current null is reached, the controlled breakdown device 13 will not again be triggered into operation. Thus, the controlled breakdown gap device 13 is provided with a sufficient predetermined voltage to cause a breakdown between the control electrode 38 and the main conducting terminal 36, which breakdown in turn permits a breakdown between the main conducting terminals 36, 37 between the time that the contacts 40, 42 of the circuit breaker 12 open and the time that the contact arm 44 reaches the phantom line position as shown in FIG. 1 to open the contacts 72, 74, 76.

A second embodiment of the present invention is illustrated in FIG. 3, wherein each a pair of switches generally designated by the numerals 92, 94 is connected in series with a corresponding one of a pair of control electrodes 48, 49. As can be seen in the aforementioned application of Hurtle, Ser. No. 542,806 and Laffetry, Pat. No. 3,030,376, the control electrodes 48, 49 are situated in the region between the main electrodes 36, 37 so that a breakdown between them will reduce the breakdown potential required for conduction across the gap between the main electrodes 36, 37.

In the embodiment of FIG. 4, the circuit breaker potential is applied between control electrode 48 and main conducting terminal 36 as well as between control electrode 49 and main conducting terminal 37. Thus, double triggering is provided.

The nature of the circuit breaker 12 and the current and potential specifications of the controlled breakdown gap device 13 may be chosen to properly handle the magnitude of electric currents and potentials involved in the circuit in which the apparatus of the present invention is to be utilized. The positions of the capacitors and resistors and the exact design details of the mechanical parts herein may be adjusted to suit the requirements of any particular implementation of the invention.

Various mechanical means may be employed to effect the opening of the switch controlling the current interruption assisting device. Various lost motion linkages provide simple means for effecting the time delay in opening the switch subsequent to opening of the breaker contacts. However, it will be appreciated that electrical circuitry, or combinations of mechanical linkage and electrical circuitry, can be used to effet the interlocking of the circuitry and the delay in opening of the switch controlling the interruption assisting device.

Thus it can be seen that the present invention provides a relatively simple and yet very effective parallel circuit electric current interrupting device which electrically couples the parallel circuit interruption-assisting device only during periods when the breaker contacts are closed. The coupling is easily effected through simple mechanical means providing a rugged and positive interlock.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In an electric circuit interrupter for controlling the flow of current in an electric circuit, the combination comprising:

(a) an electric ciruit breaker having terminals for serial connection between two points of an electric current carrying circuit and including a pair of relatively movable contacts and operating mechanism for effecting relative movement of said pair of contacts between open and closed circuit positions;

(b) a triggering current interruption assisting device. comprising a pair of main electrodes and a pair of control electrodes positioned between said main electrodes within an evacuated enclosure;

(c) parallel circuit means connecting said interruption assisting device in parallel with said circuit breaker;

((1) control connecting means connecting each of said control electrodes to a different one of said circuit breaker terminals respectively;

(c) said control connecting means including a pair of switches, each of said switches controlling the connection of a corresponding one of said control electrodes to the corresponding one of said circuit breaker terminals, and

(f) lost-motion connecting means connecting said switches to said operating mechanism of said circuit breaker, said switches being in closed position when said circuit breaker is in closed position, and said connecting means moving said switches to open circuit position a predetermined period of time after said circuit breaker contacts move toward said open position, whereby a voltage created by an are drawn between said circuit breaker contacts is applied directly between said control electrodes of said interruption assisting device and simultaneously between said main electrodes of said interruption assisting device to cause breakdown and conduction of said interruption assisting device to bypass current around said circuit breaker.

- References Cited UNITED STATES PATENTS 3,309,570 3/1967 Goldberg 317-11 3,330,992 7/1967 Perrins 317-11 JAMES D. T RAMMELL, Primary Examiner US. Cl. X.R. 307-136 

